Time-Dependent Behaviour of a Shallow Tunnel in Overconsolidated Clay

Abstract

The presence of groundwater in clayey soils is known to affect its time-dependent behaviour. This paper presents some of the results of a parametric study performed in order to evaluate the influence of the construction technique and the soil/lining relative permeability, in the time-dependent behaviour of a shallow tunnel in overconsolidated clay. The excess pore pressures generated by the excavation are analysed and the evolution of the stress-paths with time around the tunnel section is presented. The movements induced on the soil surface and in depth as well as the loads acting on the support immediately after construction and in long-term conditions are analysed. A circular tunnel excavated at a depth of 20 m was considered and the analysis was performed using a two-dimensional finite-element code that included the MIT-E3 constitutive model.